1. Field of the Invention
The present invention relates to a pump apparatus comprising, on the way of a discharge channel having an opening in the outer surface of the housing of a pump section, a reduction chamber for reducing pulsation of a hydraulic fluid pressurized by the pump section.
2. Description of Related Art
Recent automobiles are equipped with many assistant apparatuses such as a power steering apparatus and an automatic transmission apparatus, which are activated by oil pressure to assist driving operations, and a pump apparatus is installed to generate hydraulic oil pressure of such an assistant apparatus. Since the pump apparatus is installed in vehicles, it is required to be small in size and generate high oil pressure, and therefore a rotary positive displacement pump, such as a vane pump and a gear pump, is often used as a pump section for pressurizing the hydraulic oil.
In such a pump apparatus, the hydraulic oil is intermittently discharged from the pump section, and pulsation occurs in the discharged hydraulic oil. Hence, a reduction chamber for reducing the pulsation needs to be provided on the discharge side. When the reduction chamber and the pump apparatus are provided separately, the installation performance in a vehicle is poor, and therefore it is required to integrate the reduction chamber and the pump apparatus to achieve a compact structure.
As a pump apparatus capable of satisfying such a requirement for the compact structure, there is a pump apparatus that has a reduction chamber for reducing pulsation of hydraulic oil pressurized in the pump section on the way of a discharge channel having an opening in the outer surface of the housing of the pump section and is constructed to discharge the hydraulic oil whose pulsation has been reduced in the reduction chamber from the opening in the outer surface of the housing (see, for example, Japanese Patent Application Laid-Open No. 11-166483 (1999)).
In general, a pump apparatus installed in a vehicle is shipped after performing a performance inspection after assembly and removing the hydraulic oil used for the performance inspection. When shipping the pump apparatus, a dustproof cap is attached to the opening in the outer surface of the housing so as to prevent infiltration of foreign matters such as dust during the transport to a shipping destination.
However, in the pump apparatus having the reduction chamber on the way of the discharge channel as disclosed in the Japanese Patent Application Laid-Open No. 11-166483 (1999), since the configuration of the path from the pump section to the opening in the outer surface of the housing is complicated, it is difficult to perfectly remove the hydraulic oil used for the performance inspection, and consequently the pump apparatus is sometimes shipped with the hydraulic oil remaining in the reduction chamber. In this case, there was the problem that the hydraulic oil remaining in the reduction chamber flowed into the discharge channel on the opening side during the transport to the shipping destination, and the hydraulic oil flowed into the discharge channel on the opening side leaked out of the opening when a worker at the shipping destination detached the dustproof cap to install the pump apparatus in a vehicle. When such leakage of hydraulic oil occurs, various problems may be caused, for example, the periphery is soiled with the leaked hydraulic oil, and the leaked hydraulic oil drops on the floor and makes the floor slippery for the worker.
Such problems are not associated only with pump apparatuses using oil as a hydraulic fluid, and may also be caused by pump apparatuses using a liquid other than oil as a hydraulic fluid.